All weather gas generation controlled environment storage

ABSTRACT

The disclosure is of an all weather gas supply unit for delivering generally inert gas to a sealed storage structure for atmosphere control. In the system, a gas generator combustion chamber exhausts generally oxygen-free gas to a condenser and thence to an icing arrester, the condenser being cooled by ambient air in a cooling shroud system enveloping the condenser and combustion chamber, and the icing arrester serving to collect ice from the gas exhaust when the arrester is in a freezing ambient. The condenser and arrester have water collecting and draining assemblies which are kept from freezing by a heating system such as scavenger air shrouds extending from the cooling shroud. A heating system in the cooling air shroud intake keeps the exhaust in the condenser to temperatures above freezing.

United States Patent {72] lnventor Frank D. llamerski Milwaukee, Wis.[21] Appl. No. 836,063 [22] Filed June 24, 1969 [45] Patented June 29,1971 [73] Assignee A. 0. Smith Corporation Milwaukee, Wis.

[54] ALL WEATHER GAS GENERATION CONTROLLED ENVIRONMENT STORAGE 12Claims, 4 Drawing Figs.

[52] US. Cl 34/32 [51] Int. Cl F26b 3/06 [50] Field of Search 34/32,72-76; 23/281 [56] References Cited UNITED STATES PATENTS 2,746,2455/1956 Geisler et al 23/281 X 2,756,215 7/1956 Burgess 23/281 X2,787,530 4/1957 Staiger 23/281 2,876,069 3/1959 Geisler 23/2813,205,049 9/1965 Lannert 23/281 3,348,922 10/1967 Bose et a1. 23/281Primary Examiner- Edward J. Michael Attorney-Andrus, Sceales, Starke &Sawall ABSTRACT: The disclosure is of an all weather gas supply unit fordelivering generally inert gas to a sealed storage structure foratmosphere control. In the system, a gas generator combustion chamberexhausts generally oxygen-free gas to a condenser and thence to an icingarrester, the condenser PATENTEUJUHZQISYI 3,589,025

SHEET 1 [IF 2 FIG ll WM WW 21 M FUEL F J CONOEN ER j I PREMIX COMBUSTIONFLOW I I 17 T16) 22 POWER CONTROL I F I I I3 L l l \23 FUEL VALVES FIG 224f I 12 FUEL I ICING L g3 2 O 1O ARRESTER TO STORAGE I STRUCTURE EINVENTOR. FRANK D. HAMERSKI Attorneys PATENTED JUH29 I97! SHEET 2 OF 2INVENTOR. RANK D. HAMERSKI Attorneys ALL WEATHER GAS GENERATIONCONTROLLED ENVIRONMENT STORAGE BACKGROUND OF THE INVENTION Thisinvention relates to a controlled environment storage system and moreparticularly to a gas supply unit for supplying gas having minimal watervapor and minimal oxygen content to sealed storage structures in varyingweather conditions.

Perishable materials, such as animal feeds like silage, are often storedin airtight silos or other sealed storage structures in order tominimize contact between the material and oxygen from the ambient air.Accessory systems have been developed to protect the sealed structuresand the stored material. For instance, protection is needed for sealedstructures against pressuredifferentials with the ambient, which are duein part to temperature differences with the ambient. Since a pressuredifferential can cause undue stress and leakage problems, breathersystems and pressure control systems having breather valves are commonlyemployed in the unit. Often, flexible breather bags are used, whichbeing located in the head space of the silo, and being internally incommunication with the ambient atmosphere, will expand and contract inaccordance with the pressure differential to balance the differential.

In this way, entry of air from the atmosphere to the silo is restrictedand oxygen content of the storage atmosphere is minimized. Breather bagsystems provide advantage, but improved results can be obtained bypurging the sealed storage structure with a gas which is largely devoidof oxygen that is free to react. Gas burners or generators will providea gas with a high percentage of CO and N and a low percentage of CO andnear zero percentage of In theory then, it would be expected that gasgenerators could be used to further control the atmosphere in a sealedstorage unit.

As a practical matter, however, gas generators cannot simply beconnected to a storage structure and operate satisfactorily. One problemis that heat is also an undesired product of the combustion gasgenerator process and an ap preciable temperature difference between thesilo and the ambient can arise when the heated generator gas issupplied. This temperature difference can aggravate the normal pressuredifferentials between the silo and ambient, thus hampering the otherwiseadequate operation of a breather system.

The gas-generating process also generates water vapor, anotherundesirable element in the storage unit. Moisture can increase spoilageand excess moisture can actually create standing water problems in asilo.

Moisture creates problems in the generator and gas line also,particularly in freezing winter conditions. The moisture collects andfreezes within pipes and other components through which the gas passesto the silo. The operation of a gas generator can be stopped by suchfreezeups, making the generators usable only in favorable climate.

Another problem is presented in that the usual gas drying equipment, ascondensers or other heat exchangers, generally operate by expanding andcooling the gas. But in a sealed storage structure system, thetemperature of the gas is a key consideration and the removal of thewater vapor by the usual condensers would not cooperate satisfactorilywith a breather system pressure control.

The conventional equipment is also inadequate to provide for the varieddew point conditions which would exist in the storage atmosphere. Forexample, a generator gas which would be adequately dry under onetemperature in the storage structure may have an excess of water vaporunder a lower temperature and a lower dew point. No simple combinationof presently available equipment can provide a system with satisfactorycooperation between the various components in order to obtain dry gas atthe proper temperature for the variety of conditions in the storagestructure.

As a further difficulty in employinga gas generator at mosphere control,the designer is always restricted by con siderations of economy andspace. The expense of preserving the stored materials should not surpassthe expense of spoilage. Further, bulky systems are a disadvantage,especially when the generator unit is to be employed in working areas,such as near silos where space is already at a premium.

SUMMARY OF THE INVENTION The invention is directed to the solution ofthe above problems and has further advantages as described.

The structure of the invention provides a controlled atmosphere storagestructure with an all-weather gas supply unit for supplying generallyinert gas to the sealed storage structure. The gas supply unit isoperable in any climate, including freezing winter conditions. The gasis delivered with a water vapor content which will not endanger storageconditions, even when very dry gas is needed due to low dew pointconditions existing in the storage structure.

At the same time, the invention delivers the gas at a temperature nearwhatever temperature the ambient is at any moment. Thus, pressurecontrol within the storage structure is not hampered by the gas supplyunit and the unit cooperates with the breather system to obtain thedesired pressure equalization in the sealed storage unit.

Low ambient temperature operation is made possible by the provision ofantifreczeup equipment for parts subject to icing. The antifreezeupassembly is designed. to cooperate with the desired feature of gastemperature control.

The system which provides this sophisticated operation in cludes a gasgenerator having a combustion chamber which burns fuel and air andexhausts inert gas, meaning here: gas having no more than a trace ofoxygen available for oxidation. The exhaust gas is passed through acondenser which is a heat exchanger between the ambient air and theexhausted gas. Water vapor is condensed and removed as liquid and thegas is cooled to near the ambient temperature by the condenser. The gasis then passed through a defrostable icing arrester, which is disposedin the ambient air and operates to collect ice and remove water vapor ina freezing ambient.

Advantageous cost saving and compactness is served by accessoryequipment for the gas supply unit. An integral cooling air shroud andscavenger duct system provide the ambient air for cooling the condenserand for cooling the combustion chamber, and also provides the warmingair for the parts subject to icing.

In freezing weather operation, a heating element or air temperingsystem, which can be supplied with warm air by a feedback duct from thecooling air shroud, keeps the ambient air in the shroud above a minimumtemperature to protect the condenser and other elements from freezing.In winter operation of the invention, the gas is cooled to near theambient temperature by the defrostable ice arrester after the gas hasbeen partially cooled and dried by the condenser.

Thus, the gas supply unit provides an all weather system which hascomponents cooperating to provide an oxygendepleted gas, at a favorabletemperature and vapor condition to preserve the stone material and alsoto cooperate with the breather system of a sealed storage unit.

The figures illustrate the best embodiment and modifications of theinvention presently contemplated by the inventor.

FIG. I is a side elevation of the invention with parts broken away toreveal the inside structure of the storage unit;

FIG. 2 is a flow diagram showing the: essential features and operationof the invention;

FIG. 3 is a side elevational view of the gas generator with parts of thecabinet broken away to reveal the inside structure, and having certainparts shown generally in block diagram; and

FIG. 4 is a perspective view of part of a modified generator having afeedback air tempering assembly.

DESCRIPTION In the illustrated example, a sealed silo l is adapted tostore silage 2 and is exposed to the ambient environment. Above silage 2A headspace 3 exists wherein a flexible breather bag 4 of a well-knownconstruction is suspended in any suitable fashion from the roof of silo1.

Breather bag 4 is exposed internally to the ambient pressure by abreather tube 5 connected to the bag and extending through the silo roofto vent 6. Thus, bag 4 will expand and contract in response to thepressure differentials across the walls of silo l and act to balancesuch differential.

For excess pressure differentials, a relief valve 7 on the silo roofwill permit controlled ingress or egress of air to headspace 3. Valve 7is of a well-known construction and may be set to open for pressuredifferentials in the range of L5 to +3.5 inches of water.

A gas supply unit 8 is provided for storage atmosphere control inaccordance with the invention and includes an exother mic gas generator9, a defrostable ice arrester l0 and gas conduit 11. Unit 8 is disposednear silo 1 and defines a gas supply passageway ultimately reachingheadspace 3 through conduit 1 1 which is connected to silo 1.

The essential features and operation of the invention are showndiagrammatically in the flow diagram of FIG. 2. A supply of fuel, suchas propane, is contained in a fuel tank 12 and passes through a fuelflow rate control 13 to a premix chamber 14 where the fuel is mixed withair supplied from the ambient through an air volume flow rate control15.

The fuel mixture passes to a combustion chamber 16 where an ignitiondevice 17 fires to initiate the combustion. After combustion isinitiated, the process is self-sustaining and provides a heated exhaustgas comprised largely of N CO and H 0. This exhaust gas passes through acondenser 18, to a water separator and trap assembly 19, and then out ofthe generator 9 to defrostable icing arrester 10, having a water trap 20and ultimately to the storage structure.

To cool condenser 18 and combustion chamber 16, a cooling air shroud 21provides space for ambient air to flow past the condenser and combustionchamber. Blower 22 provides the air flow for shroud 21.

Protection from freezing is provided for various elements includingwater separator and trap 19, trap 20 and condenser 18. This is indicateddiagrammatically by heaters 23, which in the most advantageous structureis supplied by scavenger ducts from shroud 21 as indicated by ducts 24.

The gas supply unit 8 includes a power supply and control device whichis manually or automatically operated to start and stop the unit and itsvarious parts. The power and control unit is shown schematically asconnected to the appropriate electrically operated components.

Having enumerated the various parts which make up gas supply unit 9 andtogether define a gas flow path to the silo, the various parts will nowbe described in accordance with a particular illustrative example of theinvention.

Referring particularly to FIG. 3, gas generator 9 is disposed in anupright cabinet 25 which may be metallic and of any suitableconstruction. Several parts are numbered the same as their generalizedversions shown in the flow diagram in FIG. 2. Shown generally in blockdiagram, a fuel supply assembly 26 represents the fuel control 13,mixing chamber 14, air volume control 15 and various other elementswhich are well known and are required to provide air and fuel forcombustion chamber 16. These elements may be located in various placeswithin cabinet 25 in the actual design. Air is supplied to the devicethrough a louvered vent 27 in cabinet 25, and propane fuel is suppliedfrom a fuel tank via a gas line 28.

To provide the inert gas at the proper temperature and vapor condition,combustion chamber 16 and condenser 18 are disposed in cooling airshroud 21. Combustion chamber 16 is attached by suitable means, such assuspending rod 29 depending from the top of cabinet 25 and extendingthrough shroud 21 to attachment at the top of the combustion chamber 16.Chamber 16 is thus in a vertical position.

Combustion chamber 16 has an elongated cylindrical wall 30 with top andbottom walls 31 defining a tubular combustion chamber. A strong, heatresistant, metallic material,

such as carbon steel, is desirable for use in constructing walls 30 and31. Adequate cooling of the walls is provided by a plurality of integralfins 32 extending the length of cylindrical wall 30 and extendingradially outward therefrom in the flow path of cooling air.

The fuel mixture is passed to chamber 16 through fuel line 33 extendingfrom fuel supply assembly 26 through shroud 21 and to chamber 16 whereit connects with a fuel orifice admitting the fuel-air premix into thechamber such as by spraying the premix to obtain proper combustion.

lgnition unit 35, shown diagrammatically, provides a means of initiatingcombustion. Although it may be a pilot light device, it is shown as anelectrical ignition and is shown schematically as being electricallyconnected to a suitable control and power supply box 36. Control box 36may also contain suitable switches and motors for controlling theoperation of fuel supply assembly 26.

After ignition, the heat from combustion should sustain the reactionuntil fuel is cut off. It is contemplated that control box 36 could havea programmer for that purpose, so that the generator operatesperiodically in accordance with a desired schedule or varying conditionsin the field.

Combustion of fuel will produce an exhaust gas comprised mainly of CO Nand H 0. This exhaust will exit chamber 16 through chamber exhaustopening 37 to pipe 38 which extends downwardly to condenser 18 where itconnects to inlet opening 39 in a header 40 of the condenser.

Condenser 18 serves to reduce the gas temperature and water content. Forthis purpose it has a series of interconnected metal tubes 41 joinedtogether to provide a cooling passage for the gas. Fins 42 are welded tothe tubes and give more air-metal interface for heat exchange. At theend of bottom tube 41 an exhaust opening 43 is provided so that tubes 41and openings 39 and 43 define a gas passageway which is interconnectedinto the supply passageway of unit 8. The gas will pass into thecondenser and come in contact with the tube walls which are cooled bymeans described below. Water vapor will condense and collect on thewalls of the tubes and on the walls of parts connected down the line.The condenser is disposed at an angle to facilitate drainage.

Gas conduit 44 is connected to exhaust opening 43 and extends to waterseparator and trap assembly 19. The water separator is of a well-knownconstruction and has a collector bulb 45 disposed beneath the level ofconduit 44 and an end bell 46 on top of bulb 45. Bulb 45 and bell 46together define a closed chamber. On one side of end bell 46 there is agas inlet opening 47 to which conduit 44 opens and on the opposite sidethere is an outlet opening 48. Gas will thus pass through end bell 46from condenser 18 via conduit 44.

Condensate will drain from condenser 18 and conduit 44 to collector bulb45, where it will collect for purposes of drain ing. A drain pipe 49 isconnected to bulb 45, opening into the bottom of the bulb, and extendsto water trap 50, which is also of a well-known construction and willnot be described in detail here.

Trap 50 is subjected to the gas pressure by means of gas line 51connected between conduit 44 and the trap. A suitable water drain isconnected to the bottom of trap 50, extends through cabinet 25, andprovides a drain passageway for the water in trap 50.

To exhaust the gas from generator 9 on down the gas supply unit 8, gasconduit 52 is connected to outlet opening 48 of end bell 46 and extendsthrough cabinet 25 to icing arrester 10 where it is connected to anarrester pipe 53.

The icing arrester 10 serves to further cool the gas and in freezing orwinter ambients will operate to condense out the water vapor in the formof ice. For this purpose, arrester 10 has a defrostable chamber definedby a cylindrical sidewall 54, and end walls 55. These walls areconstructed of good heat conducting material, such as aluminum. The gasentrance is provided by an opening 56 in the forward end wall 55, whichopening is in communication with arrester pipe 53. An arrester exhaustopening 57 is in sidewall 54, and gas exhausted from generator 9 viaconduit 52 will pass through the chamber of icing arrester and contactsidewall 54. in near freezing or freezing ambients, water vapor freezeson wall 54 due to exposure to the ambient temperatures.

The defrostable feature of arrester 10 may be provided by a heating rod58 which extends the length of the chamber along the axis ofcylindricalsidewall 54. Rod 58 is an electrical conductor, having electricalresistance sufficient to serve as a heating source. Connectedelectrically to terminals on opposite ends of rod 58, are leads 59 whichextend through a control 60 to any suitable power source, thuscompleting a normally open circuit. Control 60 can be any type of switchwhich can be set to periodically close the heating rod circuit forpurposes of defrosting as needed.

When the heating rod 58 is operating, the ice collected in the chamberof icing arrester 10 will defrost and the resulting water will drain outarrester pipe 53 and flow to an arrester water trap 61 to which the pipe53 connects. Trap 61 is a wellknown device and will not be described indetail here. Trap 6] has a water drain 62 at its bottom, and is subjectto gasline pressure via line 63 connected between trap 61 and arresterpipe 53 at a point above conduit 52. Trap 61 thus operates to drainwater, but to restrict appreciable gas leakage from the system.

in accordance with the invention, gas supply unit 8 includes accessoryequipment that cooperates with the various elements which provide thegas passageway to silo 1, resulting in the desired all-weatheroperation, and the additional advantages in cooperation with breatherbag 4.

Generator 9 has a cooling air shroud 21 which serves a number offunctions in combination with the other elements of the generator.Shroud 21 has a cylindrical sidewall 64 of diameter to encompass finnedcombustion chamber 16 so as to leave a substantial annular cooling airspace. Sidewall 64 is disposed approximately coaxially with chamber 16and at con denser 18 the shroud assumes the shape of a box and extendsvertically from below the condenser to above the chamber to fullyenvelope them. The bottom of shroud 21 has an air inlet 65. At the topof the shroud, cooling air exit is permitted by an air outlet 66 whichcomprises a series of bias cuts around the circumference of sidewall 64.Top wall 67 completes the structure of shroud 21, while brackets 68 arebolted to wall 64 and cabinet 25 to secure the shroud in position. Thematerials used in the shroud structure may be any inexpensive thinmetal.

Cooling air is supplied to shroud 21 by a blower 69 con nected to shroud21 at air inlet 65. An inlet louvered vent 70 in the bottom of cabinet25 permits air entry for blower 69 and an exit louvered vent 71 incabinet 25 at the top permits air exhaust from air outlet 66.

The motor of blower 69 is electrically connected to control box 36 foroperation when generator 9 is in service. The blower has an inlet 72 atthe end opposite shroud 21 and adjacent vent 70.

When generator 9 is operating, blower 69 causes ambient air to flowthrough shroud 21 and around condenser 18 and combustion chamber 16. Theair flow cools the bottom tube 41 to within a few degrees of the ambienttemperature and still provides cooling for the upper tubes andcombustion chamber 16.

In freezing ambient conditions, condenser 18 and other parts may collectice due to air flow. For this reason, air heater 73 is provided and forthe overall operation of the system can be any heater such as anelectrical resistance element as shown. Heater 73 is disposed at airinlet 72 for blower 69 and is electrically connected to control box 36for operation with the generator 9. The operation of heater 73 iscontrolled by thermostat 74 on shroud 21 to heat the inrushing air onlyto maintain the condensate abow il'CCZll'lg temperatures, thus avoidingfreezeup. Thermostat 74 shuts heater 73 down when the shroud air is at atemperature such as +25 F. which will keep the temperature in the gaspassageway components above freezing. Housing 75 connecting to cabinet25 and to blower 69 includes a cylindrical sidewall for enclosing heater73, and for defining an air passageway from vent 70 to blower inlet 72.

When the cooling air is heated in operation of heater 73, condenser 18may not cool the gas to near the ambient temperature. However, the gaswill be cooled considerably from its high temperature achieved incombustion chamber 16. in the case of such operation in a freezingambient, further cooling of the gas is provided by icing arrester 10,and the gas will be ultimately supplied to the silo at near the ambienttemperature even in winter weather. This manner of operation avoidsfreezeup of the delivery line and still provides low dew point, inertgas delivery to the storage structure.

Also, for operation in freezing winter ambient temperature, a scavengerduct 76 and warming hood 77 are provided for water separator bulb 45 andtrap 50. lDuct 76 is a hollow conduit connecting hood 77 to shroud 21for communication with the warmed air from the shroud. For this purpose,duct 76 is attached to an appropriate opening in shroud 21 which openingis disposed near the top or above combustion chamber 16. Thus, chamber16 will warm the air when the generator is operating and part of thewarm air will be used to maintain bulb 45 and trap 50 from freezeup.

Hood 77 and duct 76 may be made of any suitable material, as metal. Toenclose separator bulb 45 and trap 50, hood 77 has top and sidewalls andis attached to cabinet 25 to define a closed box. Warm air circulationmay be assisted by cutting a hood vent 78 in one of the sidewalls of thehood and the cabinet. it is contemplated that an electrical heatingelement may be substituted for the scavenger system shown withouthampering the overall operation of the system of the invention. However,the scavenger system is advantageously efficient and an added feature ofthe invention.

A similar antifreezeup device is provided for arrester water trap 61.Warming hood 79 envelopes trap 61, has an end wall, two sidewalls, andtop and bottom walls and is connected on one end to cabinet 25 to definea closed box enveloping arrester pipe 53 and trap 61, leavingappropriate holes for extension of the various pipes and conduits. Wherecabinet 25 is connected to hood 79, an appropriate hole is cut forcommunication with a second scavenger duct 80 which is a hollow conduitmember extending to the top of shroud 21.

FIG. 4 illustrates a modified form of the invention in which a modifiedheating system for the inrush of air to shroud 21 is provided by an airtempering system. The other components of generator 9 are the same andnumbered identically in this embodiment as in the first embodiment. Theair tempering system has a feedback duct 81 extending from anappropriate opening near the top of shroud 21 to a tempering hood 82disposed at the bottom of cabinet 25 between blower 69 and cabinet 25.Hood 82 is a metal box having two chambers, a plenum chamber 83 and alower chamber 84. The chambers 83 and 84 are defined by the hood wallsand a partition 85 extending horizontally across the center of hood 82.One lower chamber wall of the hood is attached to blower 69 at its inlet72, which opens into lower chamber 84.

Feedback duct 81, which can be constructed similarly to the other ducts,provides a passageway for air warmed by combustion chamber 16 to anopening through hood 82 into plenum chamber 83.

Lower chamber 84 is adapted to conduct cooling air introduced throughambient air inlet 86 disposed at vent 70 in cabinet 25, and dischargedthrough the opening on the opposite side of hood 82, complementing andin communication with blower inlet 72.

Air tempering is provided by a cooperating pair ofdampers, a warm airdamper 87 which is normally closed and is disposed to fit in'acomplementary opening 88 in partition 85, and an ambient air damper 89fitted in lower chamber ambient air inlet 86, damper 89 being normallyopen. A common linkage 90, having an elongated metal strip link 91 orother thermostatic control in contact with the ambient air, operates thedampers. As part of linkage 90, each damper 87 and 89 has an offset rod92 clamped to the respective dampers and positioned horizontally acrossthe center thereof. Rods 92 each have an offset portion at an end wherethey are attached to opposite ends of strip link 91 to complete linkage90. The linkage may be secured in place for operation by providingopening frames 93 around the periphery of the respective damper openingsand then extending rods therethrough for a mounting arrangementpermitting rotation of the rods.

Control 91 will contract and expand according to the temperature, andthe offsets in rods 92 are adapted to translate such change in dimensioninto rotation of dampers 87 and 89. For instance, contraction of strip91 will tend to close damper 89, and simultaneously to open damper 88.In that case, warm air from plenum chamber 83 will enter lower chamber84 and will ultimately pass back through the cooling air shroud 21. Thedimensions and temperature expansion and contraction characteristics ofstrip 91 are chosen so as to keep warm air damper 88 closed until nearfreezing ambient temperatures; but for lower temperatures the stripshould contract an amount to open damper 88 an amount permitting enoughfeedbackair to mix with inrushing ambient air to keep the resultantmixture at the proper temperature in shroud 2]. These parameters canonly be determined in relation to the particular dimension and materialsused in the unit.

OVERALL OPERATION The structure of the invention provides an atmospherecontrol for a storage structure which operates in all weather conditionsand cooperates with pressure control in the storage -unit.

Operating in a warm ambient, for one situation, control device 36 can beset to periodically switch on, simultaneously, the various operatingparts of generator 9. Combustion chamber 16 then begins supplying theoxygen depleted gas which will ultimately reach silo 1. The gas passesthrough the various elements as described relative to the flow diagramof FIG. 2.

At the same time, blower 69 is switched on and cooling air shroud 21 issupplied with ambient air. The air is originally at the ambienttemperature, as air heater 73 and thermostat 74 have been set to closethe electrical heating circuit only near freezing ambient temperatures.in the embodiment of FIG. 4, the dampers 87 and 89 are in their normalpositions and feedback duct 81 is closed off from lower chamber 84 sothat the inrushing ambient air is not being mixed with warm air.

Thus, the products of combustion from chamber 16 are cooled by contactwith the walls of tubes 41 of condenser 18. Water will condense out intubes 41 and further down the line in conduit 44, to be collected bybulb 4S and ultimately drained from the system. The extent of cooling islimited byL.

the temperature of the ambient air in shroud 21 and therefore evenduring warm ambient operation, the gas will not be cooled below theambient temperature. As the gas eventually reaches hcadspace 3 of silo1, no appreciable temperature differential with the ambient will becaused and breather bag 4 will operate generally independently of gasunit 8. Further. the moisture content of the gas will have been reducedto a level whereat even for the warm ambients, moisture will notcondense out when the gas reaches hcadspace 3. As conditions change inthe silo or ambient air, the described operation of condenser 18 andcooling air shroud 21 will tend to stabilize the situation, since gasunit 8 supplies gas generally at the conditions of the ambient, andpurges the atmosphere in silo 1 of gas therein which may have been at adifferent condition.

I Arrcster 10 and the various heating arrangements for water separatorbulb 45, trap 50 and trap 61 have no vital operation in a warm ambient.As the climate approaches freezing weather, however, these parts play animportant role. First, the setting of eitherthermostst 74 for heater 73or strip link 91 and damper linkage 90 for the feedback air temperingsystem are such as to operate their respective systems to warm the airin shroud 21, maintaining the condenser temperature above freezing. inthat case, the condition of the vapor leaving condenser 18 and generator9 will not be cooledj and at the proper dew point so as to match theconditions in'rheadspace 3, since the condenser has not cooled it tonear the ambient temperature. Freezeup, of course, has been avoided incondenser 18 and conduit 44.

lcing arrester 10, however, is in contact with thefreezing ambient air,mainly by wall 54. There the gas is cooled to near the ambienttemperature, and moisture is largely removed by collecting as ice on thewalls of arrester 10. Control 60 being set to periodically close thecircuit in heating rod 58, the ice is melted at such times to defrostthe'unit and keep it operable. The gas is thus conditioned by arrester10 in winter situations, so as to generally correspond to the conditionof the ambient, and the oxygen-depleted and vapor-depleted atmosphere insilo l is maintained without causing difficulties with pressuredifferentials.

Freezeup of other vital parts is prevented by the scavenger ducts 76 andand their respective warming hoods 77 and 79. These scavenge air fromshroud 2|, which air has been warmed by cooling combustion ehamber'l6,and very efficiently prevent l'rcezcup of separator 19 with trap 50 andthe defrost trap 20. These warming systems do not appreciably interferewith the temperature control of the gas vapor. Thus, all weatheroperation is provided for generator 9 and ice arrester unit 10.

The invention described provides an atmosphere control system for astorage structure, which system operates in all weather conditions toprovide a gas that is proper for varying storage conditions andcooperates with pressure differential control in the storage structure.

The embodiments described are the best examples ofthe invention whichare presently contemplated.

The following claims define the scope of the invention.

1. A gas supply unit for a storage structure adapted to store perishablematerials and disposed in the ambient air, comprising a gas passage lineconnected to the storage structure unit, a gas generator connected tosaid line for discharge of an oxygen-depletcd gas into said line, and adefrostable icing arrester connected into said line between thegenerator and the storage structure, the arrester defining a gas passagechamber connected with said line, the arrester chamber providing an icecollecting surface in contact with said gas passing through thearrester, the surface being a heat exchanger with the ambient, thearrester having defrosting means for melting ice col: lecting on saidcollecting surface, and the arrester having a water drain to drain waterfrom the defrosted ice, whereby the gas supply unit avoids gas at nearambient temperatures even in freezing ambient.

2. The assembly of claim 1, wherein the defrostable icing arrester iscomprised of:

an outside heat conducting wall assembly defining said arrester chamberand exposed to the ambient, the wall as sembly having an inlet in gascommunication with the combustion chamber, further having an arresterexhaust outlet in gas communication with said gas passage line and thestorage structure, the wall assembly and its openings thereby defining agas passage which brings the gas in contact with the outside will forheat exchange with the ambient; and

the defrosting means being an electrical heating element disposed in thearrester chamber and having a resistance circuit with a control switchmeans for closing the circuit at preselected times in accordance withthe amount of ice collection in the chamber in freezing ambientoperation.

3. The structure defined by claim 1, wherein: the gas generator has anintegral condenser connected betweer the combustion chamber and theicing arrester for gas communication, said condenser being a heatexchanger between said gas and a cooling fluid having a temperatureabove a minimum temperature to avoid freezing of condensate in thegenerator.

4. The structure ofclaim 1, wherein the arrester has a water separatorassembly in fluid communication with said arrester chamber drain openingto drain water therefrom; and the gas unit includes a heater memberdisposed at the drain and separator assembly.

5. The structure of claim 6, wherein the generator includes a coolingair shroud enveloping the combustion chamber and providing a space forairflow past the combustion chamber the generator further includes ablower member which supplies a cooling airflow in said shroud, and saiddrain heater member comprises a warming hood enveloping the drain andseparator assembly, and a scavenger duct connected between the hood andthe shroud, the duct being a conduit connected through said shroud at aposition to accept airflow after it has flowed past at least part of thecombustion chamber, the duct defining an airflow passage from the shroudto the hood.

6. In a storage unit having a sealed storage structure for storing aperishable material, a gas generator disposed in the ambient air forsupplying gas to the atmosphere of the storage structure, the generatorcomprising:

a carbonaceous fuel burner having a combustion chamber with an exhaustend having an exhaust opening through which products of combustion of acarbonaceous fuel are expelled;

a condenser disposed adjacent the combustion chamber at the exhaust endand having a condenser inlet opening communicating with said combustionexhaust opening to define a gas passage from said exhaust opening tosaid inlet, the condenser providing a gas passageway from the inlet to acondenser outlet, which outlet is connected for gas communication withthe storage structure, and the condenser having a heat exchanger wallwith one surface in contact with the atmosphere surrounding saidcondenser and the opposite surface in contact with gas passing throughsaid condenser;

a shroud having a wall assembly enveloping the combustion chamber andcondenser and defining an air space around said chamber and condenser,the shroud having an air inlet opening at the condenser and an airoutlet opening at a chamber end opposite the exhaust end of the chamber;

a blower disposed at one ofthe shroud openings, the blower havingoperable structure which draws ambient air in and causes said air toflow in said inlet through the shroud air space and out said outlet;

the shroud having a duct opening disposed near the combustion chamberend opposite the exhaust end;

a water separator assembly connected by conduit between the condenseroutlet and the storage structure, said separator assembly having watercollecting and draining structure;

a warming hood having wall structure enveloping said water collectingand draining structure and defining an air space around said collectingand draining structure, the hood having a duct opening in its wallstructure; and

a scavenger duct connected between the shroud and hood duct openings,said scavenger duct providing an air passageway from the shroud to thehood,

7. In a storage unit having a sealed storage structure for storing aperishable material, a gas generator disposed in the ambient air forsupplying gas to the atmosphere ofthe storage structure, the generatorcomprising:

a carbonaceous fuel burner having a combustion chamber with an exhaustend having an exhaust opening through which products of combustion of acarbonaceous fuel are expelled;

a condenser disposed adjacent the combustion chamber at the exhaust endand having a condenser inlet opening communicating with said combustionexhaust opening to define a gas passage from said exhaust opening tosaid inlet, the condenser providing u gas passageway from the inlet to acondenser outlet, which outlet is connected for gas communication withthe storage structure, and the condenser having a heat exchanger wallwith one surface in contact with the atmosphere surrounding saidcondenser and the opposite surface in contact with gas passing throughsaid condenser;

a shroud having a wall assembly enveloping the combustion chamber andcondenser and defining an air space around said chamber and condenser,the shroud having an air inlet opening at the condenser and an airoutlet opening at a chamber end opposite the exhaust end of the chamber;

a blower disposed at one of the shroud openings, the blower havingoperable structure which draws ambient air in and causes said air toflow in said inlet through the shroud air space and out said outlet;

the shroud having a duct opening at. a position near the combustionchamber end opposite the exhaust end of the chamber;

a tempering hood disposed at the shroud inlet, the hood having a wallstructure defining an air chamber which is divided by a partition into aplenum chamber and another chamber, a hole being through the partition,said other chamber having a hood inlet opening and a hood outlet openingwhich is in gas communication with the shroud inlet, said plenum chamberhaving an opening through the wall structure;

a feedback duct connected between the plenum chamber opening and theshroud duct opening thus defining an air passageway between the insidesof said chamber and shroud operation;

a pair of dampers, one each disposed in said hole in the partition andthe hood inlet opening; and

a thermostatic control means for opening and closing said dampers to mixair from said plenum chamber and said other chamber in a manner whichmaintains condensate in said condenser above freezing.

8. The structure defined by claim 9, wherein the thermostatic controlmcans is a linkage assembly comprising:

a pair of offset rods, each connected on one end to a damper, offsetportions being on another end of each rod and the offsets being oppositein direction,

a heat expansiblc link connected between the offset ends of the rods,the link being exposed to the ambient temperature, said link having anabove freezing temperature dimension such as to close the damper in thepartition closed and to open the damper in the hood inlet, and the linkhaving below freezing dimensions such as to contract and draw the offsetportions toward each other thus to partially open the partition openingdamper and partially close the hood inlet damper.

9. In a sealed storage structure adapted to store perishable materialsin a controlled atmosphere, the storage structure having a breatherassembly adapted to pressurize the interior of the storage structure togenerally match the pressure of the ambient; a gas supply unit having incombination:

a gas generator having parts interconnected such that together theyprovide a gas passage leading to an exhaust conduit member at an exhaustend of the passage, said interconnected parts including: a burner at theend of the passage opposite the exhaust end, which burner exhaustsproducts of combustion of carbonaceous fuels; a condenser connected inthe passage after the burner, the condcnser having a surface which is aheat exchanger between the burner exhaust and the ambient air; a waterseparator connected in the passage after the condenser and having awater collecting and drain assembly;

an icing arrester connected for gas communication to the generator viasaid exhaust conduit, said arrester having an arrester outlet anddefining a gas passageway for the generator exhaust from the exhaustconduit to said arrester outlet, the arrester providing a heat exchangersurface in said passageway, which surface exposes the generator exhaustto the temperature of the ambient, and having a water drain assembly;

defrosting means for melting ice in the icing arrester; and

an elongated conduit connected to the arrester at the ar rester outletand providing a gas passageway to the interior of the storage structurefrom said arrester outlet.

10. The combination of claim 9 and including:

a heater disposed at the water separator; and

a heater disposed at the arrester drain assembly.

11. The structure defined by claim 9, and including a combination:

an air shroud in said generator, the shroud having wall structure whichenvelops the condenser and provides an air space around said condenser,the shroud having an inlet and an outlet which with said wall structuredefine an air flow path therebetwecn;

a blower in said generator, which blower has structure adapted to propelambient air into the shroud inlet; and an air heater in the generator,the heater being disposed at said shroud inlet and having a thermostaticmeans for maintaining the gasflow in the condenser at above freezingtemperatures. 12. The method of controlling the atmosphere in a sealedstorage structure disposed in the ambient air, the method comprising:

generating at predetermined times gaseous products of combustion ofacarbonaceous fuel by burning the fuel;

cooling said products of combustion by heat exchange with the ambientair;

heating the ambient air which cools said products when the ambient is atfreezing temperatures so as to maintain said gaseous products abovefreezing;

separating water from the products of combustion after said productshave been cooled;

then after said cooling and water separation, passing said productsthrough a second cooling device wherein the products are cooled by heatexchange with a wall surface exposing the products to ambienttemperatures including freezing temperatures;

then passing the products of combustion into the storage structure; and

defrosting the second cooling device at selected times to maintain saiddevice open to gas passage.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,589,025 Dated June 29, 1971 Inventor(s) Frank Hamerski It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 3, line 12, after "of" insert a minus sign before the "1.5"

Column 9, line 4, cancel "6" and substitute therefor (in claim 5 Signedand sealed this 21 at day of December 1 971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer ActingCommissioner of Patents FORM PO-1050 (10 69) USCOMM-DC 60376-P6D fi LISGOVERNMENT PRINTING OFFOCI: "Q9 O3I6-3ll

2. The assembly of claim 1, wherein the defrostable icing arrester iscomprised of: an outside heat conducting wall assembly defining saidarrester chamber and exposed to the ambient, the wall assembly having aninlet in gas communication with the combustion chamber, further havingan arrester exhaust outlet in gas communication with said gas passageline and the storage structure, the wall assembly and its openingsthereby defining a gas passage which brings the gas in contact with theoutside will for heat exchange with the ambient; and the defrostingmeans being an electrical heating element disposed in the arresterchamber and having a resistance circuit with a control switch means forclosing the circuit at preselected times in accordance with the amountof ice collection in the chamber in freezing ambient operation.
 3. Thestructure defined by claim 1, wherein: the gas generator has an integralcondenser connected between the combustion chamber and the icingarrester for gas communication, said condenser being a heat exchangerbetween said gas and a cooling fluid having a temperature above aminimum temperature to avoid freezing of condensate in the generator. 4.The structure of claim 1, wherein the arrester has a water separatorassembly in fluid communication with said arrester chamber drain openingto drain water therefrom; and the gas unit includes a heater memberdisposed at the drain and separator assembly.
 5. The structure of claim6, wherein the generator includes a cooling air shroud enveloping thecombustion chamber and providing a space for airflow past the combustionchamber the generator further includes a blower member which supplies acooling airflow in said shroud, and said drain heater member comprises awarming hood enveloping the drain and separator assembly, and ascavenger duct connected between the hood and the shroud, the duct beinga conduit connected through said shroud at a position to accept airflowafter it has flowed past at least part of the combustion chamber, theduct defining an airflow passage from the shroud to the hood.
 6. In astorage unit having a sealed storage structure for storing a perishablematerial, a gas generator disposed in the ambient air for supplying gasto the atmosphere of the storage structure, the generator comprising: acarbonaceous fuel burner having a combustion chamber with an exhaust endhaving an exhaust opening through which products of combustion of acarbonaceous fuel are expelled; a condenser disposed adjacent thecombustion chamber at the exhaust end and having a condenser inletopening communicating with said combustion exhaust opening to define agas passage from said exhaust opening to said inlet, the condenserproviding a gas passageway from the inlet to a condenser outlet, whichoutlet is connected for gas communication with the storage structure,and the condenser haviNg a heat exchanger wall with one surface incontact with the atmosphere surrounding said condenser and the oppositesurface in contact with gas passing through said condenser; a shroudhaving a wall assembly enveloping the combustion chamber and condenserand defining an air space around said chamber and condenser, the shroudhaving an air inlet opening at the condenser and an air outlet openingat a chamber end opposite the exhaust end of the chamber; a blowerdisposed at one of the shroud openings, the blower having operablestructure which draws ambient air in and causes said air to flow in saidinlet through the shroud air space and out said outlet; the shroudhaving a duct opening disposed near the combustion chamber end oppositethe exhaust end; a water separator assembly connected by conduit betweenthe condenser outlet and the storage structure, said separator assemblyhaving water collecting and draining structure; a warming hood havingwall structure enveloping said water collecting and draining structureand defining an air space around said collecting and draining structure,the hood having a duct opening in its wall structure; and a scavengerduct connected between the shroud and hood duct openings, said scavengerduct providing an air passageway from the shroud to the hood.
 7. In astorage unit having a sealed storage structure for storing a perishablematerial, a gas generator disposed in the ambient air for supplying gasto the atmosphere of the storage structure, the generator comprising: acarbonaceous fuel burner having a combustion chamber with an exhaust endhaving an exhaust opening through which products of combustion of acarbonaceous fuel are expelled; a condenser disposed adjacent thecombustion chamber at the exhaust end and having a condenser inletopening communicating with said combustion exhaust opening to define agas passage from said exhaust opening to said inlet, the condenserproviding a gas passageway from the inlet to a condenser outlet, whichoutlet is connected for gas communication with the storage structure,and the condenser having a heat exchanger wall with one surface incontact with the atmosphere surrounding said condenser and the oppositesurface in contact with gas passing through said condenser; a shroudhaving a wall assembly enveloping the combustion chamber and condenserand defining an air space around said chamber and condenser, the shroudhaving an air inlet opening at the condenser and an air outlet openingat a chamber end opposite the exhaust end of the chamber; a blowerdisposed at one of the shroud openings, the blower having operablestructure which draws ambient air in and causes said air to flow in saidinlet through the shroud air space and out said outlet; the shroudhaving a duct opening at a position near the combustion chamber endopposite the exhaust end of the chamber; a tempering hood disposed atthe shroud inlet, the hood having a wall structure defining an airchamber which is divided by a partition into a plenum chamber andanother chamber, a hole being through the partition, said other chamberhaving a hood inlet opening and a hood outlet opening which is in gascommunication with the shroud inlet, said plenum chamber having anopening through the wall structure; a feedback duct connected betweenthe plenum chamber opening and the shroud duct opening thus defining anair passageway between the insides of said chamber and shroud operation;a pair of dampers, one each disposed in said hole in the partition andthe hood inlet opening; and a thermostatic control means for opening andclosing said dampers to mix air from said plenum chamber and said otherchamber in a manner which maintains condensate in said condenser abovefreezing.
 8. The structure defined by claim 9, wherein the thermostaticcontrol means is a linkage assembly comprising: a pair of offset rods,each connected on one end to a damper, offset portions being oN anotherend of each rod and the offsets being opposite in direction, a heatexpansible link connected between the offset ends of the rods, the linkbeing exposed to the ambient temperature, said link having an abovefreezing temperature dimension such as to close the damper in thepartition closed and to open the damper in the hood inlet, and the linkhaving below freezing dimensions such as to contract and draw the offsetportions toward each other thus to partially open the partition openingdamper and partially close the hood inlet damper.
 9. In a sealed storagestructure adapted to store perishable materials in a controlledatmosphere, the storage structure having a breather assembly adapted topressurize the interior of the storage structure to generally match thepressure of the ambient; a gas supply unit having in combination: a gasgenerator having parts interconnected such that together they provide agas passage leading to an exhaust conduit member at an exhaust end ofthe passage, said interconnected parts including: a burner at the end ofthe passage opposite the exhaust end, which burner exhausts products ofcombustion of carbonaceous fuels; a condenser connected in the passageafter the burner, the condenser having a surface which is a heatexchanger between the burner exhaust and the ambient air; a waterseparator connected in the passage after the condenser and having awater collecting and drain assembly; an icing arrester connected for gascommunication to the generator via said exhaust conduit, said arresterhaving an arrester outlet and defining a gas passageway for thegenerator exhaust from the exhaust conduit to said arrester outlet, thearrester providing a heat exchanger surface in said passageway, whichsurface exposes the generator exhaust to the temperature of the ambient,and having a water drain assembly; defrosting means for melting ice inthe icing arrester; and an elongated conduit connected to the arresterat the arrester outlet and providing a gas passageway to the interior ofthe storage structure from said arrester outlet.
 10. The combination ofclaim 9 and including: a heater disposed at the water separator; and aheater disposed at the arrester drain assembly.
 11. The structuredefined by claim 9, and including a combination: an air shroud in saidgenerator, the shroud having wall structure which envelops the condenserand provides an air space around said condenser, the shroud having aninlet and an outlet which with said wall structure define an air flowpath therebetween; a blower in said generator, which blower hasstructure adapted to propel ambient air into the shroud inlet; and anair heater in the generator, the heater being disposed at said shroudinlet and having a thermostatic means for maintaining the gasflow in thecondenser at above freezing temperatures.
 12. The method of controllingthe atmosphere in a sealed storage structure disposed in the ambientair, the method comprising: generating at predetermined times gaseousproducts of combustion of a carbonaceous fuel by burning the fuel;cooling said products of combustion by heat exchange with the ambientair; heating the ambient air which cools said products when the ambientis at freezing temperatures so as to maintain said gaseous productsabove freezing; separating water from the products of combustion aftersaid products have been cooled; then after said cooling and waterseparation, passing said products through a second cooling devicewherein the products are cooled by heat exchange with a wall surfaceexposing the products to ambient temperatures including freezingtemperatures; then passing the products of combustion into the storagestructure; and defrosting the second cooling device at selected times tomaintain said device open to gas passage.